Various liquid crystal displays, organic EL (Electro Luminescence) displays, and inorganic EL displays are used as universal display devices in places such as inside and outside stations, factories, hospitals, and banks. With the increasing range of uses, the variety of displays is increasing. Besides, some types of displays are available at a reasonable price due to mass production.
On the one hand, important factors in using displays for industrial instruments are the continuing supply of devices and easy maintenance. If the model of a device is changed frequently or if a device is not supplied continuously, either redesign or exchange of devices is needed, which makes the cost expensive in the long run.
On the other hand, the volume of information intended to be displayed is increasing, and therefore there is a growing need for a larger screen.
When used as display units of a device, displays are sometimes called display modules to distinguish them from displays as products. In the case of an LCD (Liquid Crystal Display), for example, a display module includes: a panel that displays display data thereon; and a drive circuit that is configured to supply an electric signal to the panel. Various display modules are available on the market. Non Patent Literature 1 discloses a technique in which, when a commercially available display module is used as a display unit of a device, a display controller takes charge of smoothing out the difference in interface between the device and the display module so as to easily handle the need for redesign or exchange of display modules. The display controller stores display data input from the device in an internal or external memory, and input the display data into the display module according to the specifications of the display module (Non Patent Literature 1 below).
Meanwhile, Patent Literature 1 discloses a technique for increasing the size of a screen by using multiple display units corresponding to display modules. In Patent Literature 1, for each of multiple display units constituting a large screen, a video display apparatus retrieves data to be displayed on the display unit from display data for the entire large screen, and sends the display unit the display data with a location number for identifying the display unit (see Patent Literature 1 below).